Theme parks have come under attack for encouraging families to spend as much
as £350 to buy special tickets to allow them to jump the queues.

The cost of entrance tickets has shot up by more than 20 per cent at most leading parks over the last three years. But they also introduced many extra charges, which can send the cost of a day out for a family to as much as £500.

Most of the extra charges are voluntary, but the one that has upset most parents is the new idea of buying a special ticket that allows queue jumping. They usually take the form of a little machine which clips onto the person's belt. Tap in the ride you want to go on and it will bleep when you are allowed to go to a separate queue, which is considerably shorter than the main queue.

At Alton Towers, on top of the £38 entrance fee for an adult, the priority tickets range between £6 per person to £80 per person, if you want to queue jump all the rides.

The entrance price for Thorpe Park is also £38, but adults and children will need to spend £60 per person if they want to buy an Ultimate Fast Track machine. Legoland, which calls its machine a "queuebot" sells them for £10 per person, or £30 for a machine that gets you to the front of more rides quicker.

With family tickets – two adults and two children – costing between £90 and £108 at the leading parks, this means that it is easy to spend, £428 on the park, before any money spent on food, drink, priority parking and souvenirs.

Siobhan Freegard, the founder of the parenting website, Netmums, said: "I find it amazing that parents put up with it.

"These theme parks have become so expensive. And now they are really pushing it with these extra charges. It won't be long before there is a backlash. I stopped going some time ago with my children."

Many consumers on parenting forums have complained that the queue jumping system causes resentment among the customers.

One on Netmums said: "It is almost like two classes of people, those who can't or won't pay, and those who will. As they are walking past you to jump the queue I found it a bit cringeworthy to be honest."

Three yeas ago Which?, the consumer magazine, conducted a survey of the top six parks in Britain that charged an entrance fee. The average price of buying a ticket at the gate on the day, for one adult, was £27.50. This has climbed by 23 per cent to £33.80, a jump far in excess of inflation.

The ticket prices are cheaper if you book in advance at nearly all parks, and most offer family tickets, but these have also climbed in price significantly. The most expensive is Alton Towers at £108, or £86.40 if bought online in advance.

Merlin Entertainments owns four of the six leading parks, including Legoland, Alton Towers and Thorpe Park is responsible for introducing the queue jumping tickets into Britain. It denied that it was a way of allowing more people to crowd into the park.

A spokesman said: "Over the last three years we have invested millions in our parks, which explains why prices have gone up. But we have a proactive policy of making sure they are not as crowded as they used to be.

"Most people who buy these priority tickets do so as a special treat."